Chuck Malloch – Audio and Home Control Electronics

Seismometer Project

Posted on April 17, 2024April 17, 2024 by CBMalloch

A friend asked me if I had a seismometer. Nope. But I might be able to build one…

One approach would be to build a more traditional weight-and-spring kind of thing, but I thought I could do it more easily with a MEMS accelerometer. I had one laying around, so I decided to try it out.

I hooked up an LSM303DLH 6DOF accelerometer/magnetometer to an ESP-01 running an ESP8266 processor.

There are a few points of interest / investigation in this project:

What is the frequency response of this kind of accelerometer?
What are the frequencies of interest to this friend?
What sampling rates are possible for this device?
How to filter / smooth the raw data
Is calibration required?
How to present the data?

In this post, I’m just going to address one possibility for the last item. I will eventually log the data with timestamps into a file on a removable drive, but right now I want to see the data.

Cutting to the chase, here’s what it looks like. Click on it to see the chart move. (Whee!)

The web page is restricted to my home network, but you are welcome to the code.

Here’s a snapshot of the main Arduino program. The functions updateWebPage_root, updateWebSocket, and updateWebSocketArray are the ones you want to look at.

Chuck’s Links Page – Some items of interest to EE and CompE seniors

Posted on October 11, 2023March 31, 2024 by CBMalloch

Articles especially pertinent to Senior Design Projects

Surface-mount soldering tutorial

Don’t use Nyquist as your only criterion for choosing a sampling rate

RP2040 resources from Cornell from their microprocessor design course ECE 4760

Wearable sensor for continuous analysis of sweat

Astrophotography and the new HD Raspberry Pi Camera

Raspberry Pi HD Camera for astrophotography

AstroPitography | Dr Adam Luke Baskerville

My DIY 8″ Telescope & Raspberry Pi HQ Camera

Astrophotography with Raspberry Pi HQ Camera and Celestron Astromaster 130 EQ

New Pi camera – any good for Astrophotography?

I2CWrapper – Using microcontrollers to translate I2C for non-I2C devices

System for digital signing of photographs

… and breaking the system for digital signing of photographs

Forest-deployed wildfire sensing and reporting system

New series of ATtiny µP eliminates requirement for dedicated pins

Blogs and Vlogs

Engineering, specifically EE, CompE

Eric Bogatin – Practical EE/CompE fundamentals and practical skills

Andreas Spiess – LoRa, low-power, sensor networks, ESP8266, ESP32

David Jones – EEVblog; instrumentation, troubleshooting, repair

Bil Herd – electrical engineer, designer at Commodore; CPLD, PLL

Moritz Klein – Audio electronics

Fran Blanche – FranLab; Apollo flight computer, DSKY, FranTone audio pedals

Big Clive – tear-downs

Ben Krasnow – Applied Science; including electronics; how he built his own electron microscope

Alan [w2aew] – tutorials on components; ham radio; RF

Security

Steve Gibson – Security Now podcast – a MUST for computer security folks; good episodes on internet components

Science & Math

Michael Stevens – Vsauce, The Mind Field

Grant Sanderson – 3Blue1Brown; math concepts, including a good visualization of Fourier analysis

Ben Sparks, Holly Krieger – Numberphile; math concepts, including large numbers and number theory

Matt Parker – Stand-Up Maths, lectures at Royal Institution

Brady Heywood – Understanding Complexity, complexity theory

Grady Hillhouse – Practical Engineering, particularly civil engineering

Making, Robots, and Machinery

Adam Savage – amazing maker, MythBusters

Simone Giertz – general making, silly projects

Jeremy Fielding – general EE topics; built a cool robot arm

Tim Hunkin – very fun arcade game maker – machining tips

Internet Black Hole – Danger!

Destin Sandlin – SmarterEveryDay; how stuff works, including helicopters, nuclear subs, the James Webb space telescope

Derek Muller (PhD Physics) – Veritasium

Mark Rober – e.g. squirrel obstacle course, glitter bomb, world’s smallest Nerf gun

Markus Voelter – Omega Tau podcast; aviation, gliders, rides in fighters. Half of his podcasts are in English; the other half in German

Scary (but interesting) stuff – Don’t do this at home (nor at M5, nor for SDP)!!!

Mehdi Sadaghdar – ElectroBOOM; high-voltage stuff; fun to watch

Colin Furze – crazy powerful builds

Plasma Channel – plasma thrusters

Styro Pyro – big scary lasers

Apparatus to monitor the cycling of the hot tub pump

Posted on December 7, 2021December 7, 2021 by CBMalloch

It’s working.

I may be having a problem with my hot tub pump – it’s running with shorter cycles than I remember it. That’s better for close temperature control, but worse for stress on the motor.
I had a problem with the pump’s computer unit once before – it was overheating and cycling more and more rapidly. So now I want to monitor it to see if its cycling is getting faster.

I can’t monitor it using a current sensor, since those ones I have are rated for 10A at 120V, while the motor unit uses 15A at 120V.

So I built a monitoring system – weather sealed a 1″ piezo disk, breadboarded a JFET amplifier for it, connected it to an ESP8266 microcontroller which I programmed to take readings at 480Hz, dot-product out the components at 60Hz and 120Hz (which for some reason is stronger) and send them via WiFi to my MQTT server, from which I scoop them with a Perl script to a log file (for now). I’ve determined the best discriminant between non-running and running with a z-score of 6.6+ from each, so I know it’s pretty good.
Now I can relax for a while while the data accumulates…

Data from the 60Hz and 120Hz dot-products:

7-Dec-2021 14:02:18: home/hot_tub_motor/a02/value/couplet -> 32.839 16.014
7-Dec-2021 14:02:24: home/hot_tub_motor/a02/value/couplet -> 29.103 16.061
7-Dec-2021 14:02:29: home/hot_tub_motor/a02/value/couplet -> 29.301 16.638
7-Dec-2021 14:02:35: home/hot_tub_motor/a02/value/couplet -> 32.062 17.769
7-Dec-2021 14:02:40: home/hot_tub_motor/a02/value/couplet -> 28.854 16.440
7-Dec-2021 14:02:45: home/hot_tub_motor/a02/value/couplet -> 33.069 16.328
7-Dec-2021 14:02:51: home/hot_tub_motor/a02/value/couplet -> 28.665 17.092
7-Dec-2021 14:02:56: home/hot_tub_motor/a02/value/couplet -> 28.019 18.892
7-Dec-2021 14:03:03: home/hot_tub_motor/a02/value/couplet -> 32.541 17.647
7-Dec-2021 14:03:07: home/hot_tub_motor/a02/value/couplet -> 29.323 16.411
7-Dec-2021 14:03:12: home/hot_tub_motor/a02/value/couplet -> 69.411 58.708
7-Dec-2021 14:03:17: home/hot_tub_motor/a02/value/couplet -> 38.942 56.288
7-Dec-2021 14:03:24: home/hot_tub_motor/a02/value/couplet -> 16.419 50.588
7-Dec-2021 14:03:32: home/hot_tub_motor/a02/value/couplet -> 25.903 59.193
7-Dec-2021 14:03:33: home/hot_tub_motor/a02/value/couplet -> 70.220 61.097
7-Dec-2021 14:03:40: home/hot_tub_motor/a02/value/couplet -> 60.011 61.728
7-Dec-2021 14:03:44: home/hot_tub_motor/a02/value/couplet -> 17.743 51.550
7-Dec-2021 14:03:49: home/hot_tub_motor/a02/value/couplet -> 37.571 57.612
7-Dec-2021 14:03:55: home/hot_tub_motor/a02/value/couplet -> 72.898 57.997
7-Dec-2021 14:04:00: home/hot_tub_motor/a02/value/couplet -> 23.630 55.861
7-Dec-2021 14:04:06: home/hot_tub_motor/a02/value/couplet -> 41.698 62.395
7-Dec-2021 14:04:11: home/hot_tub_motor/a02/value/couplet -> 56.960 59.568
7-Dec-2021 14:04:18: home/hot_tub_motor/a02/value/couplet -> 15.589 50.445
7-Dec-2021 14:04:22: home/hot_tub_motor/a02/value/couplet -> 71.046 62.314
7-Dec-2021 14:04:27: home/hot_tub_motor/a02/value/couplet -> 16.098 46.108
7-Dec-2021 14:04:32: home/hot_tub_motor/a02/value/couplet -> 70.857 61.175
7-Dec-2021 14:04:39: home/hot_tub_motor/a02/value/couplet -> 16.661 53.204
7-Dec-2021 14:04:45: home/hot_tub_motor/a02/value/couplet -> 73.267 63.262
7-Dec-2021 14:04:48: home/hot_tub_motor/a02/value/couplet -> 14.290 54.907
7-Dec-2021 14:04:54: home/hot_tub_motor/a02/value/couplet -> 70.185 61.067
7-Dec-2021 14:05:01: home/hot_tub_motor/a02/value/couplet -> 22.880 57.029
7-Dec-2021 14:05:06: home/hot_tub_motor/a02/value/couplet -> 51.657 55.721
7-Dec-2021 14:05:10: home/hot_tub_motor/a02/value/couplet -> 47.116 61.623

The hot tub motor started up at 14:03:12.

Data discriminated into “off” and “on”:

About to subscribe to topic 'home/hot_tub_motor/a02/status'
7-Dec-2021 14:42:21: home/hot_tub_motor/a02/status -> 0
7-Dec-2021 14:52:23: home/hot_tub_motor/a02/status -> 1
7-Dec-2021 15:03:02: home/hot_tub_motor/a02/status -> 0

I’m not sure why the vibration is at 120Hz and not at 60Hz. I’ll have to think about AC motors and how they operate now.

Yay! Another investigation!

Erratum – Arduino external forced reset circuit

Posted on January 6, 2021January 6, 2021 by CBMalloch

My previous post (Watchdog watchdog) sought to fix a problem – the Arduino ATmega328 I was using to monitor my heating system would occasionally hang. It would remain hung despite the use of the built-in watchdog timer to reset it. I’m not sure why, but I suspect it’s related to the electrical environment. In particular, I’ve replaced the entire Arduino board, and tested the program on the bench (where it worked perfectly, resetting as intended). I tried reconfiguring the watchdog interrupt service routine to pull Arduino pin 12 low and connected that to the ~RESET line. Still no good.

Fast forward (a few years!) while I ignore the problem and manually reset the Arduino every couple days. Finally, I designed and built a new circuit to power-cycle the Arduino; it worked perfectly on the bench. But not in deployment. Rats!

So I did a little modification – I removed the MOSFET and other power-cycling components, and dedicated a pin of the ATtiny to the inverse of the power-cycling pin – it is pulled low when a reset was needed. That pin is connected to the ~RESET line on the Arduino board. It looks like this works. I’ll update this post with news, and if it looks good, with the new program and circuit documentation.

Watchdog watchdog

Posted on December 30, 2020January 1, 2021 by CBMalloch

Well. It’s been a while. Here’s what’s new:

I monitor my heating system (temperatures, zone activation) with an Arduino, and relay the values to my home monitoring system through an ESP-01 / ESP8266. The Arduino occasionally hangs up.

I have tried to fix this by checking the power supply for good clean power; by making it reboot itself every 24 hours; by enabling the ATmega328’s watchdog timer. It still hangs up.

When it is running, it flashes an LED connected to the standard pin 13 of the Arduino. I recalled seeing that a 555 timer could be used as a missing-pulse detector. This would trigger if the 1Hz flashing stops. Cool. The missing pulse detector takes its output low during pulse starvation, and takes it high during the happy times when the pulses continue. I needed to take that prolonged low value and turn it into a one-shot pulse to drop and resume the power to the Arduino, and a second 555 could be configured as a one-shot to create this pulse. I had to add a capacitor in between to prevent continuous retriggering of the second 555, which would keep the power off to the Arduino.

The circuit “1” in the schematic illustrates this setup.

I happened to have a 556 handy, which comprises the functionality of two 555 timers. The equivalent simpler circuit is “2” in the schematic.

But, duh. I’m really more of a programmer at heart. And I had some ATtiny85 chips around. So I created an Arduino program to embody all the above functionality in a much simpler circuit – “3” in the schematic.

Note: in the code and the schematic the name ATmega refers to the (processor on the) Arduino board.

Watchdog_watchdog_sch

And I put it all onto a very small solderless breadboard. Since I needed regulated 5V to feed all the components, I put standard voltage regulation onto the breadboard as well.

The Arduino program was very simple:


/*
  Watchdog_watchdog
  
  One of my Arduinos, the one that monitors temperatures and zone activations 
  in my heating system, occasionally hangs up. This despite the fact that I'm
  using the ATmega watchdog to automatically reset it if it hangs. Dunno why. 
  The power seems good and stable. I've tried replacing the ATmega chip.

  I've decided to kill a flea with a cannon. The ATmega blinks an LED at 1Hz
  to indicate that it's still alive - I call this a throbber. The ATtiny will 
  monitor the throbber and if it stops, it will power-cycle the ATmega.
  Hah.

  The MOSFET in question will be a p-channel MOSFET configured on the high side
  of the power to the ATmega; when its gate is pulled low, it allows power to 
  flow to the ATmega. The specific MOSFET I'm using is a 5LP01SP, which is a 
  p-channel device whose pins are 1=source, 2=drain, 3=gate.
  
*/

#define pdThrobber_in 3
#define pdMOSFET      4

const unsigned long resetAfter_ms = 2000UL;
unsigned long lastThrobAt_ms = 0UL;


void setup() {
  pinMode ( pdThrobber_in, INPUT );
  pinMode ( pdMOSFET, OUTPUT );
}

void loop() {
  static int throbberStatePrevious = 0;
  int throbberState = digitalRead ( pdThrobber_in );
  if ( throbberState != throbberStatePrevious ) {
    lastThrobAt_ms = millis();
    throbberStatePrevious = throbberState;
  }
  if ( ( millis() - lastThrobAt_ms ) > resetAfter_ms ) {
    // BOOM. Cause a reset
    digitalWrite ( pdMOSFET, 1 );  // turns off ATmega
    delay ( 500 );
    digitalWrite ( pdMOSFET, 0 );
    delay ( 5000 );  // time enough to let the ATmega boot up
    lastThrobAt_ms = millis();  // reset the watchdog
  }
}

ATtiny Development Board

Posted on March 21, 2019August 25, 2020 by CBMalloch

I recently had to program an ATtiny85. As I was developing, I got tired of repeatedly wiring the connections between a 6-pin ISP socket and the ATtiny, and wanted something more permanent. I found myself sucked into Eagle CAD and this is the result. It has everything necessary to program 8-pin and 14-pin Atmel microcontrollers ATtiny25, ATtiny45, and ATtiny85.

[Read More...]

Updating some, but not all, old technology

Posted on August 29, 2018August 25, 2020 by CBMalloch

Lightning strikes. It struck near me, and fried a component of my old X10 home-control system.

X10 is a power-line-based communications network. Data is sent (slowly) over the house power lines by injecting a 120 kHz signal into the 60 Hz AC signal just after the zero-crossing of that signal. One bit per cycle is sent by either adding or withholding a short pulse of the 120 kHz.

[Read More...]

Experiment with CircuitPython, Jupyter, and WordPress

Posted on August 11, 2018August 25, 2020 by CBMalloch

I’m trying to embed a Jupyter notebook page as a blog post. I saved it as html, and copied an pasted that html below. I don’t think that’s the best way to do it.

We are exploring the Adafruit Metro M4 Express

[Read More...]

EBD-USB+ Electronic Load – Testing Power Supplies and Batteries

Posted on April 14, 2018August 25, 2020 by CBMalloch

I watched a video from Andreas Speiss reviewing electronic loads, and identifying one in particular called EBD-USB+ from zketech.com and purchased through Amazon or Banggood or wherever. The software is a little hard to find, but it’s available through this link. It comes as a .rar file, which you might need to unpack with 7-zip or Winzip. You will also need the driver.

[Read More...]

Thoughts on serial communications

Posted on March 2, 2018August 25, 2020 by CBMalloch

Maybe these issues have been solved in the past. I don’t think there is necessarily a very good solution, though.

The problem is that serial communications is imperfect. Characters get messed up in transit between two devices. When they do, that in turn messes up carefully thought out protocols, like “Capture characters in a buffer until you see the linend; then process the buffer as a single message.”

[Read More...]

Articles especially pertinent to Senior Design Projects

Astrophotography and the new HD Raspberry Pi Camera

Blogs and Vlogs

Engineering, specifically EE, CompE

Security

Science & Math

Making, Robots, and Machinery

Other Sites of Topical Interest

Internet Black Hole – Danger!

Scary (but interesting) stuff – Don’t do this at home (nor at M5, nor for SDP)!!!